Ceramic is widely used in various fields such as various devices for home appliances, substrates for integrated circuits, condensers, heat-resistant tiles of space shuttles, artificial teeth, and bones by virtue of its unique strength, hardness, and chemical stability.
Recently, as a miniaturized and high-performance electronic equipment is developed, improvement of mechanical properties and thermal conductivity of ceramic materials useful as materials for substrates has been demanded. Many researches for improving the physical properties of the ceramic materials have been conducted since the mid 1900s. In recent, there have been active attempts for integration with nanotechnologies.
As nano-additives that have been commonly used for the ceramic materials, there are carbon fibers, carbon nanotubes, graphenes, and others which have been recently spotlighted. The article “Toughening in graphene ceramic composites,” Luke S. Walker, et al., ACS NANO, Vol. 5, No. 4, (2011), 3182-3190 disclosed to produce composite materials through discharge plasma sintering after homogeneously mixing silicon nitride powder and graphene oxides through ultrasonification, to provide silicon nitride nanocomposite materials having improved toughness.
However, although carbon-based nanomaterials such as carbon nanotubes and graphenes have superior mechanical, thermal and electrical properties, their properties are weak to a high temperature. Due to this disadvantage, the carbon-based nanomaterials are not suitable for reinforcing agents of high temperature materials. To the contrary, a hexagonal boron nitride nanosheet that has been recently researched has similar mechanical and thermal properties to those of graphenes, while maintaining its properties even at a high temperature. Thus, the hexagonal boron nitride nanosheet is highly expected to be used as a ceramic composite material reinforcing agent.
From the article “Fracture toughness and toughening mechanisms in a (ZrB2—SiC) composite reinforced with boron nitride nanotubes and boron nitride nanoplatelets,” Chunguang Yue, et. al., Scripta Materialia, Vol 68, (2013), 579-582, it has been confirmed that the toughness of the ceramic composite material is increased by compositing a boron nitride nanotube and a boron nitride nanosheet with a boron zirconium-silicon carbide composite material through a ball-milling. However, since the simple mixing method through the ball-milling may cause aggregation of nanomaterials having a large aspect ratio, it may restrict the improvement in the properties of the composite material. Thus, a new technology, which can homogeneously disperse boron nitride nanosheets in composite materials, has been needed.